1. Field of the Invention
This invention relates to a method of producing net structures by connecting annular net elements with connectors.
2. Description of the Prior Art
It is well known that a net structure of metal such as aluminum (a rat guard net) is an effective means against rat damages. Taking advantage of the rats' habit of not gnawing moving things, this net structure is made by connecting, in a movable manner, a plurality of annular net elements (rings) arranged lengthwise and breadthwise in a plane with connectors. If any articles to be protected against rats are covered with this net structure, the rats cannot gnaw them because the net structure trembles the instant the rats touch it.
In addition to the rat guard net, this type of net structures is adopted for fish preserves by some fish farms, and also sometimes used as a decoration net.
FIG. 11 shows an example of this type of net structure N, in which annular net elements 1 are arranged in a plurality of rows. The rows are in a staggered arrangement by half pitch per row to make each annular element 1 surrounded by six such elements and every two adjacent elements 1 are connected to each other with a connector 2.
As shown in FIG. 12, the connector 2 consists of a staple 2' which includes a pair of arm sections 2a' and a connecting section 2b' between the arm sections 2a' as shown in FIG. 12(A). To form the connector 2, the staple 2' is shaped into a loop as shown in FIG. 12(B) or both the arm sections 2a' are rounded into curl sections 2A (FIG. 12(C)) similarly to ordinary staples.
According to a prior method of producing the net structure formed of annular net elements connected by connectors, a metal strip of, for example, aluminum is first press-cut into a plurality of annular net elements such as that shown at 1. These net elements are transported with a vibrating conveyor to a connection table, where the elements are arranged in position and the two adjacent elements are connected to each other with a connector to provide a finished net structure.
As described above, the prior method requires transportation of the net elements 1 to the connection table to connect them with a connecting device of the same principle as ordinary staplers. Therefore, if each element is not in position, the staple as the connector cannot fit in the annular element, resulting in incomplete formation of the net structure.
Moreover, because each annular ring element 1 is too small and light to be transported accurately, it is often out of position on the connection table. Such out-of-position conditions not only prevent formation of the desired net structure, but also require many temporary stops of the machine to take an additional action, for example, to remove defective net structures. This causes low yield and low efficiency and impedes mass production of the net structures.